This invention relates to a novel poly(oxyalkylene) substituted aminophenol compound which is useful in the manufacture of xanthene colorants, particularly triphenylmethane derivatives such as rhodamines. The xanthene colorants exhibit improved water solubility and fugitivity.
Xanthene dyes, and in particular rhodamine dyes, are well known in the art as exemplified in the COLOR INDEX, 3rd. ed., Vol. 4 , pp. 4419-4422 (1971). These dyes range from bright red to bright bluish red, and typically fluoresce orange or red upon exposure to ultraviolet light. Rhodamine dyes have found use in a variety of applications including coloring soaps and other cleaning products, water tracing and leak detection. While the dyes have gained wide acceptance throughout the industry, they have come under suspicion as being toxic and unsuitable for use when human exposure to the dye is expected. Less toxic rhodamines have been commercialized, such as Rhodamine WT. However, Rhodamine WT has relatively poor light fastness, and tends to stain skin, clothes and equipment.
Another category of triphenylmethane type xanthene dyes is exemplified by the fluoran compounds disclosed in Farber et al., U.S. Pat. No. 3,873,573; Hatano et al., U.S. Pat. No. 4,330,473; and Zink, U.S. Pat. No. 4,806,657. The compounds are diamino-xanthene dyes having amino groups in the 3- and 7-positions. In particular, the amino group in the 7- position may be phenyl substituted. The patents also disclose p-methoxy-N-phenylaniline intermediates which may be reacted with a ketonic acid. These dyes are particularly useful as recording material, since opening the lactone ring of such compounds converts the faintly colored material to a dark green or black color.
Methods of improving the water solubiltiy or fugitivity of dyes by providing one or more poly(oxyalkylene) substituents is known in the art. Examples of "fugitive tints" are disclosed in Kuhn, U.S. Pat. No. 3,157,633; Hauser et al., U.S. Pat. No. 4,144,028; and Brendle, U.S. Pat. No. 4,167,510. The aforementioned colorants have been found to be especially useful in the textile industry for identification of fibers and yarn during weaving or tufting. The colorants are easily removed to allow the textile product to be dyed a uniform color in subsequent stages of the manufacturing process. A large number of organic dyes have been synthesized with intermediates provided with poly(oxyalkylene) substituents and include azo, methine, anthraquinone and some triphenylmethane colorants. Nevertheless, attempts to synthesize poly(oxyalkylene) substituted xanthene dyes have not heretofore met with success.
Typical prior art processes for manufacturing rhodamine dyes provide for condensing m-dialkylaminophenol with phthalic anhydride. A diagram of the synthesis of Rhodamine B, described in Venkataraman, THE CHEMISTRY OF SYNTHETIC DYES, Vol. II, pp. 750-54 (1952), is set forth below. ##STR2## In synthesizing a poly(oxyalkylene) substituted colorant, it is desirable to alkoxylate one or more of the reactants or intermediates which form the colorant. However, the intermediates used in a typical rhodamine synthesis may not be readily alkoxylated without adding poly(oxylakylene) to sites on the intermediate which participate in colorant formation. Thus, despite a strong desire to provide a poly(oxyalkylene) substituted rhodamine colorant or other poly(oxyalkylene) substituted triphenylmethane type xanthene colorants to the market, such a product has not been available.